In a related application entitled "Passive Fire Protection System for Articulating Joints & Flexible Connections", U.S. Pat. No. 07/695,296 filed May 3, 1991 of John D. Koos and Alan Ester, there is disclosed and claimed a fire protection system for the protection of articulating joints and flexible connections for a marine riser system of an offshore oil or gas rig.
The purpose of this invention is also to provide a fire protection system against flame and heat for other parts of a marine riser tensioner system of an offshore oil or gas rig.
More specifically, this invention provides fire protection for the top riser section, called a top joint or adjustable top joint, of a string of risers which has means for facilitating the connection of a riser tensioner ring to the top joint and provides fire protection for all risers which are fully or partially unprotected.
This invention will be first described in connection with the adjustable top joint and then the protection of other risers will be described.
In a marine riser system, a string of riser sections extend from a well on the ocean floor to a platform wellhead through a hole in the platform of a rig located at the water surface. Riser tensioners, usually of the pneumatic hydraulic cylindrical type, are connected between the platform and the riser string to maintain the riser string in tension at all times regardless of the rise and fall of the rig due to wave motion. The rods of the tensioner cylinders are connected to the marine riser string by means of a riser tensioner ring.
In some of these riser tensioner systems, the top joint is provided with a means to facilitate the connection of the tensioner ring to the riser string. This means is in the form of external threads or annular protrusions over a portion of the length of the top joint. The U.S. Pat. No. 4,733,919 discloses one such top joint. Another type of top joint with threads or annular protrusions is disclosed herein in connection with this invention.
While the articulated joints, flexible connections and the tensioner ring of a marine riser tensioner system may be provided with fire protection, as disclosed in the above Related Application, and while the outer surfaces of the structural members of the system may be protected by a coating of intumescent epoxy for fire and flame protection, the threaded or protruded portion of the top joint has heretofore been left unprotected against flame and heat.
Therefore, it is an object of this invention to provide a fire protection system for the adjustable top joint of those marine riser tensioner systems having means for facilitating the connection of a riser tensioner ring to the riser string.
Too, while in some systems the riser sections normally above the water may be provided with a coating of intumescent epoxy, some risers are not so protected or may be protected over only a part of their length.
Still another object of this invention, therefore, is to provide a fire protection for all unprotected or partially unprotected riser sections of a marine riser tensioner system.
In the Related Application, the flame and heat protective covers used to cover the articulated joints, flexible connections and the rods of the tensioner cylinders are "customized" to the size and length of the structural members and the articulated joints. These protective covers are also pleated to protect the rods of the tensioner cylinders.
This invention, on the other hand, provides standardized prefabricated protective jackets to protect the unprotected part of the top joint and the unprotected parts of the other risers.
It is therefore still another object of this invention to provide the adjustable top joint and other risers with standardized prefabricated jackets to protect the top joint and to protect all or part of the marine risers of a marine riser tensioner system.